code: def test_identity():
      ident = interface.IdentityOperator((3, 3))
      assert_equal(ident * [1, 2, 3], [1, 2, 3])
      assert_equal(
          ident.dot(np.arange(9).reshape(3, 3)).ravel(), np.arange(9)
      )
  
      assert_raises(ValueError, ident.matvec, [1, 2, 3, 4])
  
imports: from functools import partial
  from itertools import product
  import operator
  from pytest import raises, warns
  from numpy.testing import assert_, assert_equal
  import numpy
  import scipy.sparse
  import scipy.sparse.linalg._interface
  from scipy.sparse._sputils import matrix
label_desc: Use image node_id 2 for calling a global function with example usage: test_identity() without return types